GMW14657

Description / Abstract: This specification describes the test procedures and performance requirements used to evaluate the locking ability of preapplied adhesive coatings on threaded fasteners.

Material Description. The adhesive is mechanically applied in liquid form to the specified threads on the fastener. After drying, the fastener is clean and dry and can be handled normally until it is installed. Upon fastener installation, the adhesive will be activated and begin to cure. The fully cured properties are expected 72 h after installation. Three (3) grades of material are covered by this specification.

Grade A: Regular strength grade for use with fasteners with serviceability requirements with temperatures up to 135 °C. Lower adhesive strength allows for service removal of bolts with less potential for fastener and/or mating thread damage.

Grade B: Higher strength grade with locking/sealing performance up to 135 °C. Use of this material is not restricted to larger fastener sizes, but potential service removal concerns should be considered before use with M6 or smaller fasteners.

Grade C: Higher strength and temperature resistant grade with locking/sealing performance up to 200 °C. Use of this material is not restricted to larger fastener sizes, but potential service removal concerns should be considered before use with M6 or smaller fasteners.

Symbols. Not applicable.

Applicability. Threaded fasteners that require a preapplied adhesive for chemical locking and sealing to prevent self-loosening due to shock, vibration, and thermal effects.

Remarks. The preapplied thread locking adhesive compounds are dry to the touch and remain inert on threaded fasteners until they are engaged into the mating threads. The shearing action/forces of assembly activate the adhesive. After proper cure time and temperature, the adhesive hardens to form a chemical bond between the mating threads. This bond prevents loosening of fasteners from shock, vibration, and thermal effects.

Note: A fastener with preapplied adhesive shall not be reused.

The preapplied adhesive material approved to this specification is designed to perform up to the temperatures stated in 1.1. For severe service conditions, such as higher temperatures, vibration, and environmental conditions, it is recommended that the fastened joint be validated using intended components, preapplied material and process before release.

The performance of the preapplied adhesive material may not perform as well as expected if coated parts are exposed to excessive humidity, oil and dirt. It is recommended that coated parts be handled with care after coating. Similarly, over time, the coating material will degrade from oxidation and other environmental effects. If coated parts are to be stored for more than one (1) year, it is recommended that the appropriate performance test be performed prior to installation.

Not all finishes (coating/plating) are tested to be compatible with all GM approved preapplied adhesive materials. It is recommended that the appropriate performance test be performed to ensure compatibility.